The present invention relates to disc storage systems. More specifically, the present invention relates to a method and apparatus for adjusting the roll static angle of a disc drive suspension.
Disc drives of the xe2x80x9cWinchesterxe2x80x9d type are well known in the industry. Such drives use rigid discs coated with a magnetizable medium for storage of digital information in a plurality of circular, concentric data tracks. The discs are mounted on a spindle motor which causes the discs to spin and the surfaces of the discs to pass under respective recording heads. Each head includes a hydrodynamic (e.g. air) bearing slider and a transducer for writing information to and reading information from the disc surface. An actuator mechanism moves the heads from track to track across the surfaces of the discs under control of electronic circuitry. The actuator mechanism includes a track accessing arm and a head gimbal assembly (HGA) for each head.
The HGA generally includes a load beam and a gimbal. The load beam includes a rigid beam section to which the gimbal is attached. The rigid beam section of the load beam transfers a pre-load force from a flexible beam portion to the head which forces the head toward the disc surface. The gimbal is positioned between the rigid beam section of the load beam and the slider to provide a resilient connection that allows the slider to pitch and roll while following the typography of the disc.
One important performance-related criteria of the HGA is known as its static attitude. The static attitude of the slider refers to the positional orientation of the slider with respect to the surface of the disc over which it is flying. The slider is generally designed to fly at a predetermined orientation (typically parallel) with the surface of the disc. Deviations from this parallel relationship which result in the front and back edges of the slider being at different heights from the disc are known as pitch errors. Deviations from this parallel relationship which result in the opposite sides of the slider being at different heights from the disc are known as roll errors. Any pitch or roll error in the desired flying attitude of the slider can degrade the performance of the disc drive. As a result, it is preferable to zero the pitch and roll angles of the head when mounted to the HGA.
The load beam, as with all mechanical structures, has a resonant frequency, which can cause instability in the HGA. The first bending mode of the HGA generally causes the load beam to vibrate or move in a vertical plane or a plane that is transverse to the plane of the load beam when the load beam is symmetric about a longitudinal axis of the load beam. However, when a twist is made in the rigid beam section of the load beam about the longitudinal axis, the load beam becomes asymmetric about the longitudinal axis. As a result, the load beam will also vibrate or oscillate in a horizontal plane at the resonant frequency. This horizontal movement produces off-track errors thereby limiting the performance of the disc drive.
When the head is mounted to the load beam, it is generally oriented with non-zero roll and pitch angles. The roll and pitch angles can be forced to zero degrees using a static attitude adjust machine (SAAM). Clamping members of the SAAM attach to the rigid beam section and twist the rigid beam section along its longitudinal axis to set the roll static angle of the head to zero degrees. Prior art methods have positioned the clamping members at the extreme ends of the rigid beam section to maximize the distance separating them. The desire was to minimize the amount of twist per unit length of the rigid beam section to avoid damaging the rigid beam section. Unfortunately, these prior art methods produce HGA""s having undesirable off-track errors.
There remains a continuing need for improved methods for adjusting the roll static attitude of the load beam. In particular, there is need to improve the sensitivity of the load beam twisting by the SAAM while simultaneously reducing off-track errors resulting from the first bending mode of the HGA.
The present invention relates to a method and apparatus for providing improved roll static angle adjustment for head gimbal assemblies (HGA""s) used in a disc drive. The method of the present invention improves roll static angle adjustment of a head located at a distal end of an HGA. In the method, a high stress region is formed in the rigid beam section proximate a distal end where a distal clamping member is coupled. A proximal clamping member is coupled to the rigid beam section a distance away from the distal clamping member. Finally at least one of the distal and proximal clamping members is rotated about the longitudinal axis such that a relative angular position of the distal and proximal clamping members reaches an adjust angle resulting in a change in the roll static angle of the head.
The apparatus of the present invention is directed to a load beam of an HGA for use in a disc drive. The load beam includes a mounting portion, a flexure arm, and a rigid beam section. The mounting portion is adapted to couple the load beam to a track accessing arm of the disc drive. The flexible beam portion is attached to the mounting portion and is adapted to supply a pre-load force to a head of the HGA through the flexure arm. The rigid beam section includes a proximal end that is attached to the mounting portion, a distal end attached to the flexure arm, and a high stress region. The high stress region includes a plurality of apertures which define high stress contours of the rigid beam section where plastic deformation is desired during roll static angle adjustment.
These and various other features as well as advantages which characterize the present invention will be apparent upon reading of the following detailed description and review of the associated drawings.